The Most Common Tax Mistakes Self-Employed Tradesmen Make

This guide is part of our Tax for Tradesmen section, where we explain how tax works for self-employed tradespeople.

The most common tax mistakes tradesmen make include:

• Not saving money for tax
• Missing the Self Assessment deadline
• Poor record keeping
• Forgetting to claim expenses
• Not understanding Payments on Account
• Mixing business and personal finances

Introduction

When you’re self-employed, managing tax becomes part of running your business. Unlike employees who have tax deducted automatically through PAYE, self-employed tradesmen are responsible for calculating and paying their own tax.

Because of this, many people make mistakes during their first few years of self-employment. In most cases these mistakes aren’t intentional — they simply happen because the tax system can be confusing if you’ve never dealt with it before.

Understanding the most common tax mistakes can help you avoid unexpected bills and stay on the right side of HM Revenue & Customs.

Not Setting Aside Money for Tax

One of the most common mistakes self-employed tradesmen make is spending their full income without setting money aside for tax.

When you’re paid for a job, the money arrives in your account with no deductions. This can make it feel like the entire amount belongs to you, but in reality a portion of that money will eventually need to be paid to HM Revenue & Customs.

Many experienced tradespeople avoid this problem by setting aside around 25–30% of their profit throughout the year to cover tax and National Insurance.

As a example – Imagine a self-employed plumber who earns £45,000 in a year but doesn’t set money aside for tax.

When the tax bill arrives the following January, they suddenly owe several thousand pounds they haven’t prepared for.

Missing the Self Assessment Deadline

Every self-employed person in the UK must submit a Self Assessment tax return each year.

The key deadline is 31 January, which is when both the tax return and payment are normally due.

Missing this deadline can lead to automatic penalties from HM Revenue & Customs, even if you don’t actually owe much tax.

Keeping records organised throughout the year makes it much easier to complete the return before the deadline.

Poor Record Keeping

Many tradesmen are excellent at their work but struggle with paperwork.

Poor record keeping can cause problems such as:

• Forgetting expenses
• Losing receipts
• Miscalculating profit
• Struggling to complete tax returns

Good records should include:

• All income from jobs
• Business expenses
• Receipts and invoices

Keeping records regularly rather than trying to rebuild everything at the end of the year saves a lot of stress.

Not Claiming All Allowable Expenses

Another common mistake is simply not claiming all the expenses you’re entitled to.

Many tradespeople forget to include things like:

• Small tool purchases
• Fuel and travel costs
• Safety equipment
• Insurance
• Professional services

If these costs aren’t recorded, they can’t be deducted from your profit. This means you may end up paying more tax than necessary.

Not Understanding Payments on Account

Many self-employed people are surprised when their second tax bill appears much larger than expected.

This usually happens because of something called Payments on Account.

If your tax bill exceeds a certain amount, HM Revenue & Customs may require you to make advance payments towards the following year’s tax.

This can make the first large tax bill feel like it has doubled.

Understanding how this system works helps avoid unpleasant surprises.

Mixing Business and Personal Finances

Using one bank account for both personal and business spending can quickly become confusing.

When transactions are mixed together it becomes harder to:

• track income
• identify expenses
• prepare tax returns

Many tradespeople find it easier to open a separate bank account for business income and expenses. This keeps financial records much clearer.

Leaving Everything Until the Last Minute

Tax returns often cause stress because people leave them until the final weeks before the deadline.

This can lead to:

• rushed calculations
• missing expenses
• unnecessary pressure

Working on your accounts regularly throughout the year makes the process far easier.

Final Thoughts

Making mistakes with tax is very common when you first become self-employed. The good news is that most problems can be avoided by understanding how the system works and keeping good financial records.

By setting aside money regularly, tracking expenses properly, and submitting tax returns on time, self-employed tradesmen can manage their finances with far less stress.

Learning these basics early can also help you keep more of what you earn while staying compliant with the rules set by HM Revenue & Customs.

Written by the founder of Finance for Tradesmen, with over 30 years of experience in the electrical industry.